1. Field of the Invention
The present invention relates generally to a method to select the value of a voltage to be set at an x-ray tube of a computer tomography apparatus for medical imaging of a patient, where the x-ray tube is operated at the selected voltage value for a scan of a region of a body of the patient. The invention also concerns a computer tomography apparatus at whose x-ray tube the voltage is to be set, as well as a data medium that has a program that is executable on a computer device to perform the method.
2. Description of the Related Art
Since the beginning of x-ray computer tomography as a medical imaging technology, it has always been sought to minimize the dose of x-ray radiation applied to a patient during the course of the radiological examination of the patient. There have been various proposals for reducing the radiation dose. For example, German Published Application No. DE 199 05 974 A 1 proposes the use of diaphragms that act in the z-direction (transverse direction to the direction of plane of the x-ray image) that are adjusted during the scan so that essentially only the region of a patient that is used for the reconstruction of the medical images is ever penetrated by an x-ray beam.
In German Published Application No. DE 199 50 794 A1, diaphragms that are dynamically adjustable in the (φ-direction have been proposed that are adjusted depending on the rotation angle during the scanning process such that likewise essentially only the region of a patient that is used for the reconstruction of images is irradiated by an x-ray beam.
Furthermore, a product by the name of “CAREDose” has been developed by Siemens, in which product the tube current of the x-ray tube of the computer tomography apparatus is modulated, depending on the rotation angle and thus on the body cross section of a patient that is to be irradiated, in order to reduce the dose of x-ray radiation to be applied to a patient. For example, the tube current is reduced given x-ray projections in the anterior-posterior direction and is increased given x-ray projections in the lateral direction.